The exemplary embodiments described herein relate generally to semiconductor devices and methods for the fabrication thereof and, more specifically, to methods of using an interfacial release layer to temporarily bond a flexible semiconductor layer to a substrate for the subsequent transfer of the flexible semiconductor layer to a flexible carrier.
Flexible semiconductor layers produced by spalling techniques (described in U.S. Patent Application Publication No. 2010/0311250 A1 to Bedell et al.) can be difficult to process. Such techniques generally employ the temporary bonding of a flexible semiconductor layer to a handle substrate and subsequent separation of the flexible semiconductor layer from the handle substrate. The temporary bonding is often incompatible with various processing parameters. For example, processing of the semiconductor layer/handle substrate assembly may occur at temperatures as high as 180 degrees C. to 250 degrees C. After processing at such temperatures, separation of the semiconductor layer from the handle substrate without causing damage to the semiconductor layer may be difficult.
The difficulty in separation of the semiconductor layer from the handle substrate is generally the result of the temporary bonding utilizing easy-release tapes that are either not stable at the processing temperatures required or which lose their easy-release properties after being exposed to such temperatures. In addition, air bubbles at the tape/semiconductor layer interface are easy to form yet difficult to remove, the difficulty in removing such bubbles resulting from the tape not being be easily peeled from the semiconductor layer and repositioned without incurring damage.
Difficulty in separation of the semiconductor layer from the handle substrate may also be the result of approaches that utilize epoxies to bond the various layers of the devices. The use of epoxies may appear to be more forgiving than those that employ tapes since (unlike tapes) interfacial air bubbles may be kneaded out of the epoxy before setting occurs. Many epoxies also have the advantage of being stable to the temperatures at which processing occurs. However, adhesive bonds with epoxies are generally permanent, which thereby inhibits clean separation of the semiconductor layer from the handle substrate.